1. Field of the Invention
The present invention relates to inspection terminals for inspecting electronic chip components, and inspection methods and inspection apparatuses using the same, and more particularly, the present invention relates to an inspection terminal for inspecting an electronic chip component by bringing the inspection terminal into contact with, for example, an external electrode of the electronic chip component, and an inspection method and an inspection apparatus for inspecting the electronic chip component using the same.
2. Description of the Related Art
FIG. 9 is an illustration of an example inspection apparatus for inspecting an electronic chip component using a known inspection terminal, disclosed in Japanese Unexamined Patent Application Publication No. 10-19949. An inspection apparatus 1 includes a turntable 2 acting as a carrier unit for carrying electronic chip components 5. The turntable 2 has a plurality of depressions arranged around the periphery thereof, each defining a storing portion 3 which stores one electronic chip component 5. The electronic chip component 5 is carried around the circumference of the turntable 2 by rotating the turntable 2.
Along the carrying path of the turntable 2, the inspection apparatus 1 has an inserter unit 6 for inserting the electronic chip component 5 into the storing portion 3, an inspection unit 7 for measuring a characteristic of the component 5, and a sorter unit 8 for sorting the component 5 based on the measured characteristics of the component 5. The turntable 2 carries the electronic chip components 5 stored in the storing portions 3 from the inserter unit 6 to the inspection unit 7. As shown in FIGS. 10A and 10B, at the inspection unit 7, an inspection terminal 9 is brought into contact with a side surface of an external electrode 5a of the electronic chip component 5.
The inspection terminal 9 is cylindrical and has a linear edge portion 9a at the end thereof. The edge portion 9a has an acute angle, generally about 80 degrees. The linear portion of the edge portion 9a is brought into contact with the external electrode 5a in the widthwise direction of the external electrode 5a, that is, so as to be substantially parallel to the longitudinal direction of the entire electronic chip component 5, as shown in FIGS. 10A and 10B. The inspection terminal 9 is connected to the inspection apparatus 1 and serves as a measuring terminal for measuring a characteristic of the electronic chip component 5. For example, when the electronic chip component 5 is a chip-type capacitor, the capacitance, the insulating resistance, and so forth thereof are measured.
The external electrode 5a of the electronic chip component 5 has a multilayer structure. First, the electronic chip component 5 has an electrode, made from a metal such as Ag or Cu, baked at the end of a substrate thereof. The electronic chip component 5 also has a Ni-plated layer formed thereon for preventing electrode leaching causing the electrode to elute into a solder member during soldering, and further has a Sn-plated layer formed on the Ni-plated layer for improving solderability.
The Sn-plated layer is likely to be oxidized and accordingly has an oxide film formed on the surface thereof, sometimes causing inaccurate measurement of the characteristic. This problem however can be solved by providing the inspection terminal 9 with the edge portion 9a. That is, the edge portion 9a breaks the oxide film on the surface of the external electrode 5a and cuts into the external electrode 5a, leading to accurate measurement of the characteristic. Even when the inspection terminal 9 has dirt accumulated on the surface thereof, the dirt is removed since the surface of the inspection terminal 9a rubs against the external electrode 5a when the inspection terminal 9 cuts into the external electrode 5a. Accordingly, an incorrect measurement caused by the dirt can be prevented, since the inspection terminal 9 has little dirt on the surface of the edge portion 9a which has cut into the external electrode 5a. 
In addition, even when the electronic chip component 5 moves inside the storing portion 3, the inspection terminal 9 can be reliably brought into contact with the external electrode 5a by bringing the linear portion of the edge portion 9a into contact with the external electrode 5a so as to be substantially parallel to the widthwise direction of the external electrode 5a. In other words, since the edge portion 9a of the inspection terminal 9 has a linear shape, at least one portion of the edge portion 9a comes into contact with the external electrode 5a even when the electronic chip component 5 moves in the widthwise direction of the external electrode 5a, i.e., in the longitudinal direction of the entire electronic chip component 5. Furthermore, since the entire external electrode 5a is not totally out of contact with the inspection terminal 9 even when the electronic chip component 5 moves in the longitudinal direction of the external electrode 5a, i.e., in the widthwise direction of the entire electronic chip component 5, the inspection terminal 9 can be brought into contact with the external electrode 5a. 
However, the edge portion of the above-described inspection terminal sometimes passes through the Sn-plated layer and reaches the Ni-plated layer since the edge portion has an acute angle. If an inner electrode layer such as the Ni-plated layer is exposed to the outside as described above, the solderability may deteriorate because of a chemical reaction of the exposed inner electrode layer when the electronic chip component is soldered onto a circuit board, thereby causing a risk of poor mounting.
Also, the external electrode of the electronic chip component is rounded off in the widthwise direction thereof as shown in FIG. 10A because of its short width. As a result, the length of the contact area between the external electrode and the inspection terminal is short, and thus, the pressing force per unit length caused by the inspection terminal increases, thereby leading to a large cut-in depth of the edge portion and consequently causing the inner electrode layer to be easily exposed to the outside.
In order to overcome the problems described above, preferred embodiments of the present invention provide an inspection terminal for inspecting an electronic chip component by accurately measuring the characteristic of the component without exposing an inner electrode layer constituting an external electrode of the component to the outside, and an inspection method using such an inspection terminal.
Also, preferred embodiments of the present invention provide an inspection apparatus which allows the inspection terminal to come into reliable contact with the external electrode of the electronic chip component by using the above-described inspection terminal and inspection method.
According to a preferred embodiment of the present invention, an inspection terminal, which contacts an external electrode of an electronic chip component for measuring a characteristic of the electronic chip component, includes a liner edge portion disposed at the end of the terminal, wherein the edge portion has an obtuse angle.
In such an inspection terminal, the edge portion has an angle preferably greater than about 90xc2x0 and equal to or smaller than about 120xc2x0.
According to another preferred embodiment of the present invention, an inspection method for inspecting an electronic chip component includes the steps of preparing the inspection terminal according to the preferred embodiment described above, bringing the linear edge portion into contact with an external electrode of the electronic chip component so as to be substantially parallel to the longitudinal direction of the external electrode, and inspecting the electronic chip component in this contacting state.
According to yet another preferred embodiment of the present invention, an inspection apparatus for inspecting an electronic chip component includes a carrier unit and a plurality of storing portions located in the carrier unit, each storing and carrying one electronic chip component, wherein the electronic chip component is sucked into the storing portion in a predetermined direction so as to be positioned and then inspected by bringing the inspection terminal according to preferred embodiments described above into contact with an external electrode of the electronic chip component.
Further, the inspection apparatus according to a preferred embodiment of the present invention includes a carrier unit and a plurality of storing portions located in the carrier unit, each storing and carrying one electronic chip component, wherein the electronic chip component is sucked into the storing portion in a predetermined direction so as to be positioned and then is inspected by using the inspection method according to the preferred embodiment described above.
In such inspection apparatuses, the electronic chip component may further be sorted on the basis of the inspected result obtained by inspecting the electronic chip component by bringing the inspection terminal into contact with the external electrode.
Since the inspection terminal has a linear edge portion disposed at the end thereof such that the linear edge portion has an obtuse angle, the edge portion of the inspection terminal does not cut excessively deep into the external electrode of the electronic chip component, and cuts in to the external level to a level sufficiently deep to break the surface of the external electrode.
The angle of the edge portion is preferably greater than about 90xc2x0 and equal to or smaller about 120xc2x0 so that the edge portion of the inspection terminal appropriately cuts into the external electrode of the electronic chip component.
With the above-described inspection terminal, substantially the entire length of the linear edge portion can be brought into contact with the external electrode of the electronic chip component by bringing the linear edge portion into contact with the external electrode so as to be substantially parallel to the longitudinal direction of the external electrode, thereby leading to a reduced pressing force per unit length and thus a reduced cut-in depth of the edge portion into the external electrode. As a result, the characteristic of the electronic chip component can be measured without causing the inner electrode layer to be exposed to the outside.
Also, with the above-described inspection terminal and inspection method, the external electrode can be arranged substantially in a fixed position by storing the electronic chip component in one of the storing portions located in the carrying unit of the inspection apparatus and by positioning the electronic chip component in the storing portion by sucking it in a predetermined direction, thereby allowing the inspection terminal to come into reliable contact with the external electrode.
By sorting the electronic chip component on the basis of an accurate inspection result obtained in an above-described manner, defective products can be reliably removed.
According to preferred embodiments of the present invention, the edge portion of the inspection terminal properly cuts into the external electrode of the electronic chip component, thereby accurately measuring the characteristic of the component without being affected by an oxide film on the surface of the external electrode or dirt on the surface of the inspection terminal. In addition, by bringing the linear edge portion into contact with the external electrode so as to be substantially parallel to the longitudinal direction of the external electrode, the contact length between the edge portion and the external electrode increases, and also the cut-in depth of the edge portion cutting into the external electrode can be adjusted.
Furthermore, by sucking the electronic chip component in a predetermined direction so as to be positioned at a predetermined position in the storing portion of the carrier unit, the position of the external electrode can be determined, thereby allowing the inspection terminal to be pressed to reliably abut against the external electrode. As a result, the above-described inspection apparatus achieves a reliable and accurate measurement of the characteristic of the electronic chip component.
The above described and other features, elements, characteristics and advantages of the present invention will become clearer from the following detailed description of preferred embodiments of the present invention with reference to the accompanying drawings.